There are various dyschromatosis of the skin such as chloasma and ephelis in the field of dermatosis as well as spots and freckles in the field of beauty science. Since there are many obscure points in the action mechanism of dyschromatosis, it is known that abnormalities of hormones and ultraviolet rays from the sunlight causes stimulation, and melanine is formed and abnormally deposits in the skin. Melanine generation inhibitors are used for the cure of such dyschromatosis as the symptomatic therapy, e.g. an oral administration of a large amount of vitamin C, injecting glutathione, and regional application of ointment, cream or lotion including kojic acid, vitamin C and the derivative thereof or cysteine. However, an adequate bleaching effect has not been obtained by these treatments.
On the other hand, in Europe and U.S.A., hydroquinone and derivatives thereof, which are known as melanine generation inhibitors, are used for the purpose of bleaching erythema dyschromium perstans.
However, the onset of the effect was very slow when the hydroquinone derivatives were used and the bleaching effect was not enough. Although the bleaching effect was tentatively admitted in hydroquinone itself, application of the hydroquinone derivatives are limited because of safety problems. Several investigations were carried out for ingredients which could reduce the side effect of the hydroquinone and have an excellent bleaching effect, but the ingredients which have an adequate effect and are safe have not been obtained.